1. Field of the Invention
The preset invention relates to a controller for controlling a machine such as a robot and a machine tool, and capable of being in wireless communication with an operation panel used to teach the machine, and also relates to a wireless module and a wireless repeater.
2. Description of the Related Art
When a machine such as a robot or a CNC machine tool is to be operated or taught, a wireless operation panel, capable of being in wireless communication with a controller of the machine, may be used. For example, JP 2007-233817 A discloses an automatic machine system including: a mechanical unit having one or more drive mechanism; a controller for controlling driving of the mechanical unit; and a teaching device for operating the mechanical unit. This document describes that the teaching device includes: a teaching device communication part configured to wirelessly communicate with the controller; and a first LIVE signal monitoring part configured to monitor a LIVE signal at constant time intervals in the teaching device communication part, and that the controller includes: a controller communication part configured to wirelessly communicate with the teaching device; a second LIVE signal monitoring part configured to monitor a LIVE signal at constant time intervals in the controller communication part; and a driving part configured to drive the mechanical unit based on a command signal from the teaching device received in the controller communication part.
Further, JP 2011-000652 A discloses a robot control system, in which a portable teaching pendant is wirelessly communicated with a robot controller, so that a robot can be controlled based on a command from the teaching pendant.
On the other hand, it is a well-known technique to detect deterioration of a receiving sensitivity of wireless communication, and switch a wireless channel from one to the other. For example, JP 2015-201728 A discloses a device control system including first, second and third devices, and a controller configured to control the devices by wireless communication, in which the controller is wirelessly communicated with the first device, the first device is wirelessly communicated with the second device, and the second device is wirelessly communicated with the third device. This document describes that, when the third device detects that the receiving sensitivity of the wireless communication is deteriorated, the second and third devices enter a channel change mode in which any control by the controller is not accepted, and then a wireless channel to be used between the second and third devices is changed.
Generally, when the robot or the CNC machine tool is operated or taught by using the wireless operation panel, and the wireless communication between the operation panel and the controller of the machine is interrupted, the motion of the machine is forcibly stopped and the teaching operation is interrupted, for safety. However, in a factory or field where the wireless communication is congested, the wireless communication may be often interrupted, and the teaching operation may be interrupted.
As one method for solving the above problem, an area where the wireless operation panel can be used may be limited within a predetermined distance (e.g., five meters) from a wireless access point in order to stabilize the wireless communication. However, in such a method, the usable area of the operation panel may be unduly limited, and the merit of wireless operation panel may be diminished.